This invention relates to an environment control unit for an airplane, more specifically, to an energy-saving control unit for environment, such as temperature, pressure or oxygen partial pressure in an airplane.
An airplane is generally provided with an environment control unit for the airplane. The environment control unit extracts compressed air of high-temperature and high-pressure from an engine or an auxiliary power portion, to regulate temperature and pressure with an air conditioning portion and then to supply the regulated air to a pressurized chamber such as a cabin or a cockpit. The environment control unit serves a variety of roles, such as to control pressure in a pressurized chamber, to supply oxygen to the pressurized chamber comfortable enough for humans, to regulate humidity in the pressurized chamber and to control air conditioning in the pressurized chamber.
The above-mentioned air conditioning portion, for example, one comprises an air cycle machine and the other that does not comprise any air cycle machine wherein the former comprises an air cycle machine is so arranged that air extracted from an engine is regulated for temperature and pressure and the regulated air is supplied to a pressurized chamber by the use of the air cycle machine where a compressor is uniaxially connected with a turbine and the latter one that does not comprise any air cycle machine is so arranged that air extracted from an engine is pre-refrigerated with a heat exchanger and supplied to a pressurized chamber. The air in the pressurized chamber is further refrigerated by the use of a vapor cycle machine mainly comprising a coolant cycle circuit having the capacity to deal with the maximum air conditioning load.
However, the amount of air extracted from an engine and consumed by the above-mentioned environment control unit accounts for about 3 percent of usual air-flow rate of the engine, which is considered to be a serious penalty. More specifically, a hundred-passenger airplane requires about 100 (lb./min) of the maximum amount of air during the maximum air conditioning load. In addition, about 1% of the air-flow rate of the engine is extracted from the engine in order to prevent explosion due to lightning or short circuit if there exists fuel vapor in an inflammable portion, such as a fuel tank. This penalty of air to be extracted directly results in deterioration in propulsive force or fuel efficiency.
For a conventional environment control unit it is difficult to provide the pressurized chamber with enough humidity, which makes passengers uncomfortable such as being thirsty.
Further, recent trends make a jet engine highly bypassed, which makes it difficult to extract a lot of air from the engine.
In order to solve the above problems the present claimed invention intends to provide an environment control unit for an airplane which can cut down an amount of air extracted so as to improve fuel efficiency and produce required cooling capacity with a simple arrangement.
The environment control unit for an airplane in accordance with the present claimed invention is so arranged that air of high-temperature and high-pressure is extracted from an engine or an auxiliary power portion of an airplane. The extracted air is regulated in temperature and pressure by an air conditioning portion and then the regulated air is supplied to a pressurized chamber. The extracted air is characterized by air expelled from the pressurized chamber or air drawn out of the pressurized chamber is separated into air enriched with nitrogen and air enriched with oxygen. The air enriched with oxygen is supplied to the pressurized chamber again and the air enriched with nitrogen is supplied to an inflammable portion such as a fuel tank.
In accordance with the arrangement, oxygen alone out of the air drawn from the pressurized chamber is supplied to the pressurized chamber again. This makes it possible to maintain oxygen concentration at a level sufficient for passengers in the pressurized chamber be comfortable even though an amount of air to be extracted for supplying fresh air is reduced by the maximum of 30 percent. In addition, it is possible to prevent explosion in an inflammable portion, such as a fuel tank, without the necessity of air to being extracted exceeding the amount necessary for air conditioning, namely, without deteriorating propulsive force nor fuel efficiency. It improves safety of the airplane that air enriched with nitrogen is supplied to an inflammable portion. As a result, it is possible to reduce the amount of air to be extracted significantly without deteriorating the reliability of the airplane nor comfort for the passengers, thereby to improve fuel efficiency and propulsive force.
Especially, that the air in the pressurized chamber whose temperature and pressure has once been regulated is utilized makes it possible to reduce the burden for the air conditioning portion significantly when compared with a case in which the air of high-temperature and high-pressure is regulated from the outset.
In case the environment control unit is provided with an auxiliary air conditioning portion that refrigerates air drawn from the pressurized chamber to a circulation line and supplies the air to the pressurized chamber again through the circulation line. This is effective if the air enriched with oxygen is supplied to the pressurized chamber by making use of the circulation line of the auxiliary air conditioning portion. If the air drawn from the pressurized chamber to the circulation line is refrigerated by a vapor cycle system, it is possible to reduce amount of air extracted from the engine significantly.
An example embodiment represented is air exhausted from the pressurized chamber or air drawn out of the pressurized chamber is separated into air enriched with nitrogen and air enriched with oxygen and vapor using a permeable membrane which can selectively permeate a molecule by compressing the air. In this case it is possible to keep humidity in the pressurized chamber at a suitable level so as to prevent for passengers from being uncomfortable by feeling thirsty.
Another example embodiment is represented by air exhausted from the pressurized chamber or air drawn out of the pressurized chamber is separated into air enriched with nitrogen and air enriched with oxygen and vapor by the use of a material which can selectively adsorb a molecule.
In this case it is preferable that a plurality of materials that selectively adsorb molecules are provided and used in turns.